Demodectic Mange

By January 10, 2012 July 14th, 2012 Interesting Cases
Willow - note the red lesion on the medial (towards the middle of the body) aspect of the eye

‘Willow’ is a very sweet, 10 month old, female spayed German Shepherd. She presented for a one week history of progressive hair loss beside her eye. The area was not itchy, and ‘Willow’ was not bothered by it. She was otherwise doing well, eating and drinking normally, and was a very active girl.

Upon examination, the area appeared to be alopecic (hairless), with very minimal erythema (redness), and a small amount of scabbing. The rest of her coat/skin appeared to be in great condition. Initial rule-outs for a small patch of hair loss in a dog Willow’s age would be Demodicosis (Demodex – a tiny mange mite that burrows beneath the skin), Dermatophytosis (also known as ringworm, a fungal infection that may occur in dogs, cats and even people!), localized pyoderma (a bacterial skin infection), or trauma or injury. Given the fact that Willow did not have a history of an injury, we decided to focus on mites and ringworm, and started with a skin scraping, with the plan for a fungal culture if the scraping was negative.

A skin scraping is a simple diagnostic test performed on an animal when mites, fungus or other infectious agents are suspected. The affected skin may be squeezed or pulled taut, while a scalpel blade is gently scraped across the skin surface, yielding skin cells, hair and dander. The sample is transferred to a microscope slide containing mineral oil and examined under a microscope. A small skin irritation may be left behind following a skin scraping, but this should heal quickly and does not require any treatment.

Performing a skin scraping on an alopecic area of skin

When we examined Willow’s sample under the microscope, multiple Demodex mites were found! Overgrowth of this skin mite leads to hair loss, scaling of the skin, variable redness and irritation, and occasionally pruritus (itchiness).

Adult Demodex mite visible at 10x magnification under the microscope

Some facts about Demodex:

  • Although a normal inhabitant of canine skin, overgrowth leading to clinical signs may occur secondary to stress, poor nutrition, or immunosuppression
  • Genetic factors may also play a role in overgrowth

Secondary infection of affected areas is common, and antibiotics are often prescribed to kill off the bacteria

  • There are 2 forms of Demodex – localized and generalized. Localized may appear as 1 to 5 areas of patchy alopecia (hair loss), most commonly on the face (although could be anywhere on the body). Generalized is classified by more than 5 areas of alopecia, and often involves large areas of the body. Affected skin may become lichenified (thickened), hyperpigemented (dark), crusted, or ulcerated
  • Treatment for the localized form includes treatment of any predisposing factors (e.g. higher quality diet, vitamin supplementation, etc). Antibiotic therapy is recommended to treat any secondary bacterial infection, and scrubbing with a Benzoyl Peroxide shampoo will also keep infection under control. Most of these cases resolve within 4-8 weeks time.
  • Treatment for the generalized form also involves correction of predisposing factors and resolving secondary infection with antibiotics. Miticidal treatment (‘mite killing’) is also necessary, and oral Ivermectin is the drug of choice, and treatment is given for weeks to months, until repeat skin scrapings are negative.

Fortunately for Willow, her very localized form will likely heal very well with antibiotics and shampoo therapy. She is a very healthy dog, on a high quality diet, so no immediate corrections to her every day care were necessary. Wish her luck for a very speedy recovery!